hierarchical nanoporous activated carbon as potential ... · using bio-derived food waste namely...
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Hierarchical nanoporous activated carbon as potential electrode materials for high performance electrochemical supercapacitor
T. Kesavan, T. Partheeban, M. Vivekanantha, M. Kundu, G. Maduraiveeran* and
M. Sasidharan*
Research Institute & Department of Chemistry, SRM Institute of Science and Technology, Kattankulathur, Chennai-603 203, Tamil Nadu, India.
*Corresponding Authors: [email protected] (GM) and [email protected] (MS)
Abstract
Recently, biomass-derived activated carbon nanomaterials represent a potential candidate in
achieving sustainable and low-cost energy storage devices. Herein, we report a facile synthesis
of hierarchical nanoporous activated carbon (NAC) by template-free and cost effective approach
using bio-derived food waste namely “Indian Cake Rusk” (ICR) and its application in high
performance supercapacitance for the first time. The influence of carbon activation process over
the physicochemical properties, morphological structure, as well as supercapacitive performance
was systematically studied. When used as an electrode in a supercapacitor, the as-synthesized
NAC material offered a high specific capacitance of 381.0 F g-1 at a current density of 1.7 A g-1
with an impressive 95 % capacity retention even after 6000 cycles using 1.0 M H2SO4
electrolyte. The NAC material also furnished a maximum energy density of 47.1 Wh kg-1 and
power density of 22644.0 W kg-1 which is higher than the existing carbon based electrode using
1.0 M LiPF6 electrolyte in symmetric supercapacitor. The superior electrochemical performance
of NAC material is ascribed to huge BET surface area (1413.0 m2 g-1), hierarchical
micro/nanoporosity, and good electrical conductivity which could serve as a promising carbon
material for advanced applications in energy, environmental, and biomedical fields.
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Keywords: Nanoporous activated carbon, High specific capacitance, Supercapacitors, Template-
free synthesis, Indian Cake Rusk.
1. Introduction
Owing to the ever growing energy demand, electrochemical energy storage systems with higher
energy and power densities such as lithium-ion batteries (LIBs), supercapacitors (SCs), etc. have
attracted tremendous attention [1,2]. In recent years, electrochemical supercapacitors have
received a great interest as a renowned power sources because of their advantages of high power
density coupled with extended cycle life, simple configuration, and easy mode of operation [3-7].
Although, electrochemical supercapacitors are widely used for numerous portable applications in
the field of electronics, power backup, memory systems, etc. and they face tough challenges for
producing high energy density supercapacitors in comparison to batteries.8,9 In an effort to
improve the energy density, nanostructured carbon based electrodes have played a major role
among various electrode materials due to its low-cost, high electrical conductivity, and good
durability. Generally, carbonaceous materials with high porosity and large surface area (1000-
1500 m2/g) deliver the energy density of ∼5.0 Wh kg-1 and gravimetric capacitance of ~120.0 Fg-
1. In this context, several carbon nanostructures such as grapheme [10,11], carbon nanotubes
[12,13] and carbon nanofibers [14,15] having a high surface area of ≥1500.0 m2g-1 were
investigated for supercapacitor applications. However, the forbidden production cost and
attaining high pure material still remain a challenging task towards commercialization. Thus, the
recent research efforts were widely focussed on the carbon based/derived materials having
advantageous attributes like tuneable pore size, high surface area, low cost, and environmental
benignity [16-18].
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In search for better carbonaceous materials, activated carbons derived from various
natural sources, food waste, bio wastes, etc. have been investigated extensively to find suitable
carbon materials [19]. Impressed with low cost factor, high surface area, and environmental
sustainability, biomass derived activated carbon materials are exceptionally attractive for energy
storage applications [20]. While chemical etching approach is often used to prepare porous
activated carbon through etching of metal or silica present in the metal organic framework
(MOF) [21,22] the method generally involves multistep synthesis and unfriendly etching
process. In this context, synthesis of biomass derived activated carbon is considered as a cost
effective strategy where the presence of biomolecules create numerous pores on the carbon
surface during high temperature activation [19,23]. Natural raw materials, including banana peel
[24], human hair [25], corncobs [26], teakwood sawdust [27], coir pith [28], rice husks [23],
etc.[29-33] have been used to obtain the porous activated carbons materials using various
chemical activation agents [34-40]. Therefore, developing a simple synthetic strategy using
abundance low-cost precursors for the production of porous structured carbon nanomaterials
with high surface area still remains a mainstream research.
Herein, we demonstrate for the first time a facile, cost-effective, and template-free large
scale synthetic strategy for novel hierarchical CN material from food waste of Indian Cake Rusk
(ICR) for application in high performance supercapacitor. The prime advantages of this study
includes (i) a facile and effective synthetic strategy; (ii) high surface to volume ratio, economic
and inexpensive sustainable resource of food waste as the precursor; (iii) high porosity with an
average pore diameter of ~3 nm without using any template agents; (iv) can be integrated either
as three-electrode or two-electrode configurations towards super capacitance application and (v)
exhibits the best maximum energy density of 47.1 Wh kg-1 and power density of 22644.0 W kg-1
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due to synergistic effect arising from large surface area and hierarchical nanoporous structure.
The present investigation will endow with new opportunity for the large-scale production of
highly mesoporous NAC from biomass for stimulating environmental and energy applications.
2. Experimental section
2.1. Synthesis of CN materials
In a typical synthesis of carbon material, the collected Indian Cake Rusk (ICR) food waste from
Bakery was ground well using mortar and pestle to obtain a fine powder. The powder was then
annealed in an alumina crucible at 450 oC for 4.0 h using a tubular furnace (Carbolite furnace,
UK) under N2 atmosphere at a ramp rate of 5 oC min-1 and the resultant carbon powder was
collected after cooling down the furnace to room temperature. In order to activate the obtained
carbon, it was mixed well with KOH (Alfa Aesar) in a stoichiometric ratio of 1:3. Finally, the
mixed powder was transferred to an alumina crucible and again annealed at 750 oC for 3 h in an
inert atmosphere. After cooling the furnace, the carbon material was collected, washed
thoroughly with pure water till the combined washings attain pH ~7.0. Finally, the activated
carbon material was collected by centrifugation and dried at 60 °C for overnight in a hot air
oven.
2.2. Physiochemical characterization
Powder X-ray diffraction (XRD) pattern was recorded with a Philips XRD ‘X’PERT PRO
diffractometer with Cu Kα rays (λ = 1.5418 Å). FT-IR spectrum was carried out with a BRUKER
OPTIK spectrometer, GMBH, Germany (Model No. TENSOR 27) using KBr pellet technique.
Raman measurements were performed using Renishaw (UK) spectrometer with a incident
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wavelength laser light of 632.8 nm. Surface area measurements were performed with autosorb
IQ series (Quantachrome Instruments). Field emission scanning electron microscopic (FESEM)
measurement was accomplished using of FEI Quanta FEG 200 HR-SEM after coating desired
carbon samples on sample stub and transmission electron microscopic (TEM) images were
recorded with a JEOL (JEM-2100 Plus) operating at 200 kV by coating test carbon sample on a
copper grid.
2.3. Electrochemical characterization
High-pure stainless steel foil with a thickness of 0.04 mm (SS 304, Alfa Aesar) was thoroughly
polished with a emery paper followed by washing with pure water and acetone, and subsequently
dried up in an oven at 60 °C for 3h. The working electrodes were constructed by modifying the
foil (geometrical surface area of ~1.0 cm2) with slurry containing 85 wt.% of as-synthesized
porous activated carbon, 10wt.% of Super P carbon (Alfa Aesar) and 5 wt.% of polyvinylidene
difluoride (PVDF) (Alfa Aesar) in N-methyl-2-pyrrolidone solvent (NMP) (Alfa Aesar) and then
dried at 120 °C under vacuum for 12 h. The mass of the active electrode materials was calculated
to be ~1.2 mg/cm2. The electrochemical properties were evaluated in a three-electrode
configuration by using platinum (Pt) as a counter electrode, saturated calomel electrode (SCE) as
a reference electrode and 1 M H2SO4 as an electrolyte in the potential window of -0.3 − 0.9 V.
Whereas coin type symmetrical supercapacitor was assembled in an argon-filled glove box
(M’BRAUN, Germany) with <1.0 ppm of oxygen and moisture content. LiPF6 salt dissolved in
EC:DMC solvents (1:1 vol%) was used as an electrolyte and polypropylene was used as a
separator in symmetrical supercapacitors. Electrochemical measurements were performed in the
potential window of 0.0 − 2.5 V using a Biologic workstation (VSP-300). The electrochemical
impedance spectroscopic (EIS) measurement was performed in the frequency range of 10 mHz –
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100 kHz. Discharge specific capacitance (SC) of the activated porous carbon material was
estimated by means of the following equation for three electrode system:
SC = I t / (m ∆V) ----------- (1) And the specific energy (SE) and specific power (SP) of a supercapacitor were estimated using
the following equations [41,42].
SE = (It∆V/m)/2 ----------- (2)
SP = (I∆V/m)/2 ----------- (3)
Where, "I" refers the current in ampere used for charge/discharge cycling, "t" presents the time
required for discharge, "m" means the mass in grams of the active carbon material and "∆V" is
the operating potential window in ‘volt’ for the charge or discharge. Discharge specific
capacitance (SC) value of the porous activated carbon electrode for two electrode system was
measured using the following equation [43]:
SC = 4 I t/m∆V ----------- (4)
The values of energy density and power density for the as-developed activated porous carbon
(NAC) material were estimated using the following equation [44,45],
Energy density = 1/2 C * ∆V2 * 1/3.6 ----------- (5)
Power density = E/∆t*3600 ----------- (6)
Where, "C" represents the specific capacitance, "∆V" refers the potential window, "E" presents
the energy density and "t" the discharge time in seconds.
3. Results and discussion
As a class of biomass, ICR mainly contains wheat flour which has high surface area, large
surface to volume ratio, and huge porosity. Schematic representation for the synthesis NAC
material from food waste of ICR is presented in Scheme 1. The hierarchical nanoporous-
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structured activated carbon material was produced without using any sacrificial templates simply
by thermal annealing (carbonization) and followed by chemical activation process at 750 °C.
Fig. 1a shows the X-ray diffraction patterns of the NAC materials obtained prior to- and after
KOH activation process, indicating a low degree of crystallinity. The characteristic diffraction
peaks observed at 25.0 and 43.0 2θ corresponding to (002) and (100) planes indicate a typical
layered structure with short-range order. As shown in Fig. 1a, the crystallinity of the NAC
materials is improved after KOH treatment due to encryption of ordered nanoporous structure on
the NAC materials at high temperature treatment. The nature of functional groups present on the
carbon surface was identified with the help of FTIR spectroscopy. Fig. 1b shows the FTIR
spectra of the NAC developed before and after KOH activation process clearly exhibiting the
presence of functional groups such as –OH, −CH, −C=C−, −CN, etc. The characteristic peak for
O−H stretching frequency was centered at 3438.0 cm-1 for the unactivated carbon samples, which
had shifted to 3409.0 cm-1 after KOH activation process. The C−H and C=C stretching frequency
were also observed at ~2922.0 cm-1 and ~1590.0 cm-1 for both the materials indicating moderate
graphite like extended conjugation. Furthermore, the existence of −C≡N group on carbon matrix
might be originated from N-containing biomass constitutents.
The Raman spectra of the developed NC material before and after KOH activation are
shown in Fig. 1c. The resonance peaks observed at 1348.0 cm-1 and 1590.0 cm-1 for both raw
and activated materials show characteristic D and G bands. In addition, the presence of D band
(defects) in the graphitic lattice represent the A1g symmetry while the existence of single
crystalline carbon atoms in the sp2 hybridization of the layered graphitic structure show E2g
mode.46 The G band intensity is relatively higher than that of D band intensity representing an
enhancement of the graphitic structure with fewer defect sites in the NAC materials than of the
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corresponding materials without KOH activation [47]. In order to evaluate textural properties
such as porosity, pore volume, and BET surface area, the NAC material and prior activation
material was subjected to nitrogen adsorption-desorption measurements (Fig. 1d). The N2
isotherm was found to be typical Type I isotherm according to IUPAC classification. The BET
surface area of NAC material was found to be 1413.0 m2 g-1 with a pore volume of 0.737 cm3 g-1
which is significantly higher (∼24 times) than that of carbon material prior to KOH activation
(surface area (58.0 m2 g-1)). Furthermore, the shape of nitrogen adsorption/desorption isotherm
indicate that majority of pores are micropores with small portion of mesopores. It is presumed
that the release of high gaseous product during KOH activation process is the key factor to
achieve high surface area porous carbon compared to prior to activation sample and also there is
no change in crystal structure for the both samples which is evident by XRD (Fig. 1a), the
enhance the electrochemical performance is mainly due to the huge surface area and porosity of
the NAC material. The electrolyte ions transportation is mainly determined by porosity, pore size
of the material, such pores are considered to be beneficial for the fast movement of ions between
the electrolyte and the active material to obtain enhanced electro kinetics. Pore size distribution
curve further shows (Fig. 1d, inset) that non-uniform mesopores with diameter in the range of
∼1.8 nm to ∼ 5.5 nm located in the NAC. The value of apparent density was also calculated as
0.61, 0.45, 0.04 and 0.12 kg/m3 for graphite, graphene, single walled carbon nanotubes and NAC
material, respectively. A NAC material with mesopores and micropores well-distributed, which
permits active ions in the micropores results shortening the transportation time and low-resistant
ion transport paths more favorable ideal for EDLCs. Thus the combination of microporous,
mesoporous textural features coupled with high BET surface would be anticipated to enhance
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electrochemical performance such as specific capacitance, cycle life stability, energy density,
and power density.
The surface morphology of the NAC was investigated with TEM and FESEM techniques.
Further confirmation of various elements present in the porous carbon was obtained by EDAX
(Fig. S1). The elemental analysis confirms the presence of C, O and N in the NAC. Fig. 2a-c
presents the TEM images of the NAC and average mesopore size was calculated to be ~3.0 nm,
respectively. Interestingly, nanoporous structures were also heavily dispersed with a uniform
distribution as displayed in Fig. 2c and Fig. S2. Fig. 2d shows a typical selected area electron
diffraction (SAED) pattern of the NAC. The SAED diffuse ring patterns appeared without any
bright spots, revealing the polycrystalline nature of the NAC as observed from the XRD pattern
(Fig. 1a).
The XPS measurements were also performed to characterize the surface elemental
composition of the NAC material. As shown in Fig. 3a, the XPS survey spectra confirmed the
presence of C, O, and N in the NAC material. Fig. 3b shows the XPS spectra of C 1s which
showed four-peaks located at ~284.8, ~285.2, ~288.6 and ~288.2 eV, corresponding to the
presence of sp2 hybridized C-C, C-O, C=O, and O=C-O groups. Further, O 1s spectrum of Fig.
3c depicts two-peaks located at ~531.3 and ~532.1, due to the presence of different oxygen
functional groups of O=C-O and C=O groups. Fig. 3d displays the N 1s spectra showed three-
peaks which are located at ~398.9, ~399.2, and ~400.3 eV, corresponding to the presence
nitrogen functionalities such as pyridinic-N, pyrrolic-N and graphitic N. These results clearly
reveal that the developed NAC material also possessed the nitrogen species as evidenced in the
FTIR (Fig. 1b) and EDAX (Fig. S1) studies. The presence of nitrogen in the NAC material could
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play a major role on the enhancement of the electronic conductivity and pseudo-capacitive
characteristics [32,46,48–49].
The electrochemical supercapacitive performance of the NAC was investigated using
cyclic voltammetric (CV) and galvanostatic charge-discharge studies both in three-electrode
system using aqueous 1.0 M H2SO4 electrolyte and two-electrode set-up with non-aqueous
electrolyte containing 1.0 M LiPF6 salt. In the three-electrode system, the electrochemical
supercapacitance study was performed in the operating potential window from −0.3 to 0.9 V vs
SCE in 1.0 M H2SO4. Fig. 4a shows the CV curves of NAC constructed electrode before (black
curve) and after activation (red curve) at a scan rate of 20 mV s-1. The rectangular shape of
voltammogram revealed an ideal electrochemical double layer capacitance (EDLC) behavior for
carbons both before and after activation step. Nevertheless, the pseudo-capacitive behavior was
also observed in the potential range of 0.1 − 0.4 V which may be caused due to the presence of
heteroatoms (nitrogen) on the surface of carbon materials as evidenced from FTIR (Fig. 1b),
EDAX (Fig. S1), and XPS (Fig. 3d). As expected, the KOH activated NAC exhibited higher
capacitance compared to unactivated carbon sample as shown in Fig. 4a. Huge surface area
coupled with nano-macro pore architecture of NAC perhaps help high charge storage as seen
from the area of CV curve in Fig. 4a. Fig. 4b depicts the CV curves of the NAC recorded in 1.0
M H2SO4 electrolyte at various scan rates varying from 10.0 mV s-1 to 200.0 mV s-1. The
rectangular shape of the CVs exhibited a replicate image of cathodic and anodic parts,
confirming the ideal capacitive behavior. The voltammograms of the present NAC materials also
indicated monotonically increasing peak current with rise of scan rate as displayed in Fig. S2. It
is noteworthy to mention that even at higher scan rates the characteristic rectangular feature
remains very stable, thus demonstrating a superior rate capability and reversibility of the ICR-
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derived carbon electrodes. The surface adsorption-desorption properties of the present system
obtained from Fig. S3, showed a near linearity due to the non-Faradaic surface adsorption-
desorption process over the porous carbon electrode [50,51]. As shown in Fig. S4, the
synthesized NAC materials exhibited higher double layer capacitive behavior in comparison to
other carbon materials such as graphite, graphene, and single walled carbon nanotubes, due to
the ascription of high electrochemical active surface area of NAC material.
The typical galvanostatic charge-discharge (CD) study was also used to investigate the
capacitive behavior of the developed NAC materials. Fig. 4c shows a typical EDLC behavior of
the NAC electrodes before (black curve) and after (red curve) the KOH activation process using
aqueous 1.0 M H2SO4 electrolyte at an applied current density of 1.7 A g-1. The unactivated
carbon material showed a linear CD curve with a lower specific capacitance of 28.0 F g-1 at a
current density of 1.7 A g-1. However, the NAC electrode (red curve) exhibited a slightly non-
linear behavior with time, exhibiting two plateaus, one during the charging (~0.35 V) and other
at discharging (~0.23 V) process possibly due to the presence of heteroatoms on the surface of
carbon electrodes [32] as observed in the CD curves of Fig. 4c and Fig. S3. Thus, the present
NAC electrode exhibited a high specific capacitance of 381.0 F g-1 at a current density of 1.7 A
g-1 which is more than ~10.0 times higher than that of the corresponding unactivated carbon as
depicted in Fig. 4c. The impressive specific capacitance of the present NAC electrode is ascribed
to their high surface area, hierarchical interconnected micro/nano-pores and facile electrode
kinetics and the performance of present NAC surpass the previous reports on supercapacitors
using biomass-based carbon electrodes as shown in Table 1.
In order to further understand the rate capability of ICR-derived NAC electrode, the
charge-discharge profiles were recorded at different current densities ranging from 1.7 A g−1 to
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83.3 A g−1 (Fig. 4d). The specific capacitance values of the present electrode were calculated to
be 381.0, 281.0, 243.0, 208.0, 139.0, and 70.0 F g-1 at applied constant current densities of 1.7,
4.2, 8.3, 16.7, 41.7, and 83.3 A g-1, respectively as presented in Fig. 5a. It is seen that the
specific capacitance was decreased from 381.0 F g-1 to 70.0 F g-1 by increasing the current
density probably due to pulverization of active materials at higher current density [41,62]. For
any practical applications, both energy density and power density are two central factors. Fig. 5b
shows the Ragone plot of the carbon electrode under present investigation, where the specific
energy decreases with the increasing specific power exhibiting a typical supercapacitor behavior.
The specific energy values were 74.0, 56.3, 48.5, 41.0, 27.5, and 13.5 Wh kg-1 corresponding to
the specific power values of 1.0, 2.5, 5.0, 10.0, 25.0, and 50.0 kW kg-1, respectively, which are
higher in comparison to the formerly reported values using NAC material obtained from
different sources (Table 1). The improved specific power of the developed NAC electrode is
solely attributed to the high specific capacitance and cell voltage.
To operate supercapacitors for high power applications, cycle life is one of the major
detrimental electrode properties. In this context, to investigate the stability and durability of the
as-developed NAC electrode, cycle life study was performed by subjecting to a constant applied
current density of 1.7 A g-1 and the data is shown in Fig. 5c. The specific capacitance of the
carbon electrode under scrutiny was slightly decreased to 381.0 F g-1 from 422.0 F g-1 after
performing continuous 250.0 cycles and thereafter, the specific capacitance (381.0 F g-1) was
maintained at the same level for over 6000 cycles as presented in Fig. 5c. The capacity retention
and columbic efficiency were found to be more than 95.0 % and ~99.5 %, respectively,
demonstrating a superior electrochemical performance and excellent durability of the developed
NAC electrode in the present study. Fig. 5d shows the Nyquist plots of fresh and cycled NAC
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electrodes. The Nyquist plots show semi-circle at high and middle frequency region and a linear
slope at the low frequency region representing the contributions from the solution resistance (Rs),
charge transfer resistance (Rct) and diffusion kinetics. In the high frequency region, low solution
resistance was observed for cycled NAC electrode when compared to the corresponding fresh
NAC electrode, showing high electronic conductivity. At the low frequency region, the value of
Rct was significantly decreased to 10.4 Ω from 18.0 Ω after cycling for 6000 cycles due to its
improved electronic conductivity. As depicted in Fig. 5d, the Warburg line also confirmed the
double layer capacitance behavior and ionic diffusion at the electrode and electrolyte interface
[61].
Furthermore, the ICR-derived NAC electrode was also investigated for symmetrical
supercapacitors using non-aqueous electrolyte containing 1.0 M LiPF6 salt dissolved in ethylene
carbonate/dimethyl carbonate solvents (EC:DMC, 1:1 volume rato). It is widely recognized that
a broad working voltage window is required in order to enhance the energy density as in the case
of non-aqueous electrolyte with symmetrical supercapacitors [63-65]. The CVs of the NAC
electrode were recorded in the voltage window of 0.0 - 2.5 V at different scan rates from 10.0
mV s−1 to 200.0 mV s−1 (Fig. 6a). The NAC electrode displayed a rectangular voltammogram
feature irrespective of the applied scan rate as shown in Fig. 6a. As the scan rate increases,
current density was also increased linearly, implying a surface adsorption-desorption process of
the NAC electrode similar to results obtained with an aqueous electrolyte (Fig. S5). Fig. 6b
presents the galvanostatic charge-discharge profiles of the carbon electrode by applying various
current densities starting from 0.35 A g−1 to 17.8 A g−1. The symmetrical supercapacitive
characteristics of the NAC electrode are also in good agreement with double layer supercapacitor
shown in Fig. 4. As displayed in Fig. S6, the NAC demonstrated a specific capacitance of 217.0
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F g−1 at a current density of 0.35 A g−1. Furthermore, the NAC electrode exhibited specific
capacitances of 217.0, 184.0, 143.0, 109.0, 69.0, and 29.0 F g−1 at the constant applied current
densities of 0.35, 0.7, 1.75, 3.57, 7.0, and 17.8 A g−1, respectively (Fig. 6c).
Fig. 6d shows the Ragone plot of the NAC electrode. The values of energy density and
power density of the ICR-derived NAC electrode were 47.1, 38.9, 31.0, 23.7, 15.0, and 6.3 Wh
kg−1; and 446.1, 870.5, 2234.2, 4481.1, 8982.0 and 22644.0 W kg−1, respectively. The NAC
electrode demonstrated a maximum energy density and power density of 47.1 Wh kg−1 and
22644.0 W kg−1, respectively. It is observed that two electrode systems using non-aqueous
electrolyte achieved a higher energy density and power density when compared to the three-
electrode system with an aqueous electrolyte because of its high operating potential window. It is
remarkable that the present biomass derived NAC delivered a maximum energy density of 47.1
Wh kg-1and power density also increased to 8982.0 W kg-1 at an energy density of 15.0 Wh kg-1.
The superior supercapacitance performance of present NAC also compared with the reported
biomass based carbon electrode materials as shown in Table 1. The significantly improved
performance of the NAC electrode is ascribed to the following factors: (i) the synthesized
nanoporous-structured carbon materials may offer beneficial physiochemical properties such as
huge surface area of 1413.0 m2 g-1, hierarchical porous structure with a pore volume of 0.737
cm3 g-1, elevated electronic conductivity (Rct: 27.5 Ω) and high apparent density of 0.12 kg/m3;
(ii) The NAC materials may afford more accessible active sites and adsorption on double sides,
facilitating high performance electrochemical characteristics; and (iii) the design of two
electrode symmetrical electrochemical storage system with NAC electrode in a wide voltage
window (Fig. 6). The porous-structured 2-D materials highly permits active ions in the
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micropores, results shortening the transportation time and low-resistant ion transport paths more
favorable ideal for EDLCs [30,32,33].
Fig. 7a shows the long-term cycle life study of the NAC electrode over 1000 cycles at a
current density of 0.35 A g-1. The initial specific capacitance of the NAC electrode was ~213.0 F
g-1 which gradually decreased to 160.0 F g-1 upon continuous cycling of the electrode. About
75.0 % retention of the specific capacitance was attained at the NAC electrode and lower
retention is ascribed to decomposition of the electrolyte in the two electrode system. Fig. 7b
shows the Nyquist plot of the NAC in symmetrical two electrode system. Semicircle present at
higher frequency region (Rct) of the cycled electrode was high (75.0 Ω) in comparison to the
fresh electrode (27.5 Ω). The electronic conductivity of the NAC electrode was decreased after
running 1000 cycles which may be due to the decomposition of electrolyte during continuous
cycling [66].
4. Conclusion
In summary, we have successfully developed a simple but effective template-free strategy for the
large-scale synthesis of well-ordered nanoporous activated carbon material directly from food
waste of ICR for application in high-performance supercapacitor. Activation of carbon materials
played a critical role in enhancing the specific surface area, porosity vis-à-vis electrochemical
performance. The as-developed NAC material possessed a high surface area of 1413.0 m2 g-1
than the correponding inactivated carbon samples. The present NAC electrode delivered a high
specific capacitance of 381.0 F g-1 at 1.7 A g-1 and showed a remarkable capacity retention with
almost 100 % columbic efficiency after 6000 charge-discharge cycles in 1.0 M H2SO4. ICR-
derived NAC electrode also delivered a high energy density and power density of 47.1 Wh kg-1
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and 22644 W kg-1, respectively in 1.0 M LiPF6 in symmetrical supercapacitor configuration.
High porosity and huge surface area coupled with high electrical conductivities are reasoned for
significant improvement in the supercapacitive performance. We strongly believe that the present
study would offer a new prospect for fabrication of high-performance carbon based electrode
materials with promising applications in fields of supercapacitor, battery, adsorption technology,
and catalysis.
Acknowledgements
The authors acknowledge Ministry of New and Renewable Energy (MNRE), Govt. of India for
financial assistance (No.31/03/2014-15/PVSE-R&D). T.K. thanks to Council of Scientific and
Industrial Research (CSIR) for providing Senior Research Fellowship (SRF). The authors also
thanks to DST-FIST (fund for improvement of S&T infrastructure) for financial assistance for
Department of Chemistry, SRM Institute of Science and Technology, No.SR/FST/CST-
266/2015(c).
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References:
[1] J. R Miller, P. Simon, Electrochemical capacitors for energy management, Science 321 (2008) 651–652.
[2] S. Sarangapani, B. V. Tilak, C. P. Chen, Materials for electrochemical capacitors, J. Electrochem. Soc. 143 (1996) 3791–3799.
[3] B. E. Conway, Electrochemical supercapacitors scientific fundamentals and technological applications, (1999) ISBN 978-1-4757-3058-6.
[4] S. S.Thind, X. Chang, J. S.Wentzell, A. Chen, High-performance supercapacitor based on tantalum iridium oxides supported on tungsten oxide nanoplatelets, Electrochem. Commun. 67 (2016) 1–5.
[5] Y. Ma, H. Chang, M. Zhang, Y. Chen, Graphene-based materials for lithium-ion hybrid supercapacitors, Adv. Mater. 27 (2015) 5296–5308.
[6] V. Aravindan, J. Gnanaraj, Y. S. Lee, S. Madhavi, Insertion-type electrodes for nonaqueous li-ion capacitors, Chem. Rev. 114 (2014) 11619–11635.
[7] T. Abbasi, S. A. Abbasi, Decarbonization of fossil fuels as a strategy to control global warming, renewable, Sustain. Energy Rev. 15 (2011) 1828–1834.
[8] L. L. Zhang, X. S. Zhao, Carbon-based materials as supercapacitor electrodes, Chem. Soc. Rev. 38 (2009) 2520–2531.
[9] Q. Wang, J. Yan, Z. Fan, Carbon materials for high volumetric performance supercapacitors: design, progress, challenges and opportunities, Energy Environ. Sci. 9 (2016) 729–762.
[10] M. D. Stoller, S. Park, Y. Zhu, J. An, R. S. Ruoff, Graphene-based ultracapacitors, Nano Lett. 8 (2008) 3498–3502.
[11] S. Boopathi, A. R. Thiruppathi, A. Chen, From graphite to interconnected reduced graphene oxide: one-pot synthesis and supercapacitor application, Chem. Commun. 53 (2017) 7828–7831.
[12] R. H. Baughman, A. A. Zakhidov, W. A, De Heer, Carbon nanotubes-the route toward applications, Science 297 (2002) 787–792.
[13] H. Pan, J. Li, Y. Feng, Carbon nanotubes for supercapacitor, Nanoscale Res. Lett. 5 (2010) 654–668.
[14] K. Wang, Y. Wang, Y. Wang, E. Hosono, H. Zhou, Mesoporous carbon nanofibers for supercapacitor application, J. Phys. Chem. C 113 (2009) 1093–1097.
18
[15] Y. Liu, J. Zhou, L. Chen, P. Zhang, W. Fu, H. Zhao, Y. Ma, X. Pan, Z. Zhang, W. Han, E. Xie, Highly flexible free standing porous carbon nanofibers for electrodes materials of high-performance all-carbon supercapacitors, ACS Appl. Mater. Interfaces 7 (2015) 23515–23520.
[16] E. Frackowiak, F. Beguin, Carbon materials for the electrochemical storage of energy in capacitors, Carbon 39 (2001) 937–950.
[17] A. G. Pandolfo, A. F. Hollenkamp, Carbon properties and their role in supercapacitors, J. Power Sources 157 (2006) 11–27.
[18] E. Frackowiak, Carbon materials for supercapacitor application, Phys. Chem. Chem. Phys. 9 (2007) 1774–1785.
[19] J. Wang, P. Nie, B. Ding, S. Dong, X. Hao, H. Doua, X. Zhang, Biomass derived carbon for energy storage devices, J. Mater. Chem. A 5 (2017) 2411–2428.
[20] M-X. Liu, L-Y. Chen, D-Z. Zhu, H. Duan, W. Xiong, Z-J. Xu, L-H Gan, L-W. Chen, Zinc tartrate oriented hydrothermal synthesis of microporous carbons for high performance supercapacitor electrodes, Chin. Chem. Lett. 27 (2016) 399–404.
[21] O. Fleker, A. Borenstein, R. Lavi, L. Benisvy, S. Ruthstein, D. Aurbach, Preparation and properties of metal organic framework/activated carbon composite materials, Langmuir 32 (2016) 4935–4944.
[22] M-H. Kim, K-B. Kim, S-M. Park, K. C. Roh, Hierarchically structured activated carbon for ultracapacitors, Sci. Rep. 6 (2016) 21182.
[23] C. Kunfeng, X. Dongfeng, Multiple functional biomass‐derived activated carbon materials for aqueous supercapacitors, lithium‐ion capacitors and lithium‐sulfur batteries, Chin. J. Chem. 35 (2017) 861–866.
[24] V. Subramanian, C. Luo, A. M. Stephan, K. S. Nahm, S. Thomas, B. Wei, Supercapacitors from activated carbon derived from banana fibers, J. Phys. Chem. C 111 (2007) 7527–7531.
[25] K.R. Saravanan, N. Kalaiselvi, Nitrogen containing bio-carbon as a potential anode for lithium batteries, Carbon 81 (2015) 43–53.
[26] B. Li, F. Dai, Q. Xiao, L. Yang, J. Shen, C. Zhang, M. Cai, Nitrogen-doped activated carbon for a high energy hybrid supercapacitor, Ener. Environ. Sci. 9 (2016) 102–106.
[27] A. Jain, S. Jayaraman, U. Ulaganathan, R. Balasubramanian, A. Aravindan, M. P. Srinivasan, S. Madhavi, Highly mesoporous carbon from teak wood sawdust as prospective electrode for the construction of high energy li-ion capacitors, Electrochim. Acta 228 (2017) 131–138.
19
[28] V. Mullaivananathan, R. Sathish, N. Kalaiselvi, Coir pith derived bio-carbon: demonstration of potential anode behavior in lithium-ion batteries, Electrochim. Acta 225 (2017) 143–150.
[29] L. Sun, C. Tian, M. Li, X. Meng, L. Wang, R. Wang, J. Yin, H. Fu, From coconut shell to porous graphene-like nanosheets for high-power supercapacitors, J. Mater. Chem. A 1 (2013) 6462–6470.
[30] M. Xu, T. Liang, M. Shi, H. Chen, Graphene-like two-dimensional materials, Chem. Rev. 113 (2013) 3766–3798.
[31] S. Ucar, M. Erdem, T. Tay, S. Karagoz, Preparation and characterization of activated carbon produced from pomegranate seeds by ZnCl2 activation, Appl. Surf. Sci. 255 (2009) 8890–8896.
[32] M. Karnan, K. Subramani, N. Sudhan, N. Ilayaraja, M. Sathish, Aloe vera derived activated high-surface-area carbon for flexible and high-energy supercapacitors, ACS Appl. Mater. Interfaces 8 (2016) 35191–35202.
[33] C. Zhan, X. Yu, Q. Liang, W. Liu, Y. Wang, R. Lv, Z-H. Huang, F. Kang, Flour food Waste derived activated carbon for high-performance supercapacitors, RSC Adv. 6 (2016) 89391–89396.
[34] J. Yan, Q. Wang, T. Wei, Z. Fan, Supercapacitors: recent advances in design and fabrication of electrochemical supercapacitors with high energy densities. Adv. Energy Mater. 4 (2014) 1300816.
[35] J. Hayashi, A. Kazehaya, K. Muroyama, A. P. Watkinson, Preparation of activated carbon from lignin by chemical activation, Carbon 38 (2000) 1873–1878.
[36] M. S. Solum, R. J. Pugmire, M. Jagtoyen, F. Derbyshire, Evolution of carbon structure in chemically activated wood, Carbon 33 (1995) 1247–1254.
[37] D. Hulicova-Jurcakova, A. M. Puziy, O. I. Poddubnaya, F. Suárez-García, J. M. D. Tascón, G. Q. Lu, Highly stable performance of supercapacitors from phosphorus-enriched carbons, J. Am. Chem. Soc. 131 (2009) 5026–5027.
[38] P. Cheng, T. Li, H. Yu, L. Zhi, Z. Liu, Z. Lei, Biomass-derived carbon fiber aerogel as a binder-free electrode for high-rate supercapacitors, J. Phys. Chem. C 120 (2016) 2079–2086.
[39] L. Zhang, F. Zhang, X. Yang, K. Leng, Y. Huang, Y. Chen, High-performance supercapacitor electrode materials prepared from various pollens, Small 9 (2013) 1342–1347.
[40] Y. Lu, S. Zhang, J. Yin, C. Bai, J.Zhang, Y. Li, Y. Yang, Z. Ge, M. Zhang, L. Wei. M. Ma, Y. Ma, Y. Chen, Mesoporous activated carbon materials with ultrahigh mesopore volume and effective specific surface area for high performance supercapacitors, Carbon 124 (2017) 64–71.
20
[41] Y. Munaiah, B. G. S. Raj, T. P. Kumar, P. Ragupathy, Facile synthesis of hollow sphere amorphous MnO2: the formation mechanism, morphology and effect of a bivalent cation-containing electrolyte on its supercapacitive behavior, J. Mater. Chem. A 1 (2013) 4300–4306.
[42] P. K. Nayak, N. Munichandraiah, Simultaneous electrodeposition of MnO2 and Mn(OH )2 for supercapacitor studies, Electrochem. Solid-State Lett. 12 (2009) A115–A119.
[43] J. Han, L. L. Zhang, S. Lee, J. Oh, K-S. Lee, J. R. Potts, J. Ji, X. Zhao, R. S. Ruoff, S. Park, Generation of B-doped graphene nanoplatelets using a solution process and their supercapacitor applications, ACS Nano 7 (2013) 19–26.
[44] X. Tiana, H. Ma, Z. Li, S. Yan, L. Ma, F. Yu, G. Wang, X. Guo, Y. Ma, C. Wong, Flute type micropores activated carbon from cotton stalk for high performance supercapacitors, J. Power Sources 359 (2017) 88–96.
[45] Y. Li, G. Wang, T. Wei, Z. Fan, P. Yan, Nitrogen and sulfur co-doped porous carbon nanosheets derived from willow catkin for supercapacitors, Nano Energy 19 (2016) 165–175.
[46] M. P. Kumar, T. Kesavan, G. Kalita, P. Ragupathy, T. N. Narayanan, D. K. Pattanayak, On the large capacitance of nitrogen doped graphene derived by a facile route, RSC Adv. 4 (2014) 38689–38697.
[47] A. C. Ferrari, J. C. Meyer, V. Scardaci, C. Casiraghi, M. Lazzeri, F. Mauri, S. Piscanec, D. Jiang, K. S. Novoselov, S. Roth, A. K. Geim, Raman spectrum of graphene and graphene layers, Phys. Rev. Lett. 97 (2006) 187401.
[48] L. Miao, D. Zhu, Y. Zhao, M. Liu, H. Duan, W. Xiong, Q. Zhu, L. Li, Y. Lv, L. Gan, Design of carbon materials with ultramicro-, supermicro- and mesopores using solvent- and self-template strategy for supercapacitors, Micropor. Mesopor. Mater. 253 (2017) 1–9.
[49] W-J. Lu, S-Z. Huang, L. Miao, M-X. Liu, D-Z. Zhu, L-C. Li, H. Duan, Z-J. Xu, L-H. Gan, Synthesis of MnO2/N-doped ultramicroporous carbon nanospheres for high-performance supercapacitor electrodes, Chin. Chem. Lett. 28 (2017) 1324–1329.
[50] P. Ragupathy, H. N. Vasan, N. Munichandraiah, Synthesis and characterization of nano- MnO2 for electrochemical supercapacitor studies, J. Electrochem. Soc. 155 (2008) A34–A40.
[51] P. Ragupathy, D. H. Park, G. Campet, H. N. Vasan, S-J. Hwang, J-H. Choy, N. Munichandraiah, Remarkable capacity retention of nanostructured manganese oxide upon cycling as an electrode material for supercapacitor, J. Phys. Chem. C 113 (2009) 6303–6309.
[52] E. Y. L. Teo, L. Muniandy, E-P. Ng, F. Adam, A. R. Mohamed, R. Jose, K. F. Chong, High surface area activated carbon from rice husk as a high performance supercapacitor electrode, Electrochim. Acta 192 (2016) 110–119.
21
[53] J. Hou, C. Cao, X. Ma, F. Idress, B. Xu, X. Hao, W. Lin, From rice bran to high energy density supercapacitors: a new route to control porous structure of 3D carbon, Sci. Rep. 4 (2014) 7260.
[54] H. Feng, H. Hu, H. Dong, Y. Xiao, Y. Cai, B. Lei, Y. Liu, M. Zheng, Hierarchical structured carbon derived from bagasse wastes: a simple and efficient synthesis route and its improved electrochemical properties for high-performance supercapacitors, J. Power Sources 302 (2016) 164–173.
[55] Y. Gong, D. Li, C. Luo, Q. Fu, C. Pan, Highly porous graphitic biomass carbon as advanced electrode materials for supercapacitors, Green Chem.19 (2017) 4132–4140.
[56] C-K. Sim, S. R. Majid, N. Z. Mahmood, Electrochemical performance of activated carbon derived from treated food-waste, Int. J. Electrochem. Sci. 10 (2015) 10157–10172.
[57] I. I. G. Inal, S. M. Holmes, A. Banford, Z. Aktas, The performance of supercapacitor electrodes developed from chemically activated carbon produced from waste tea, Appl. Surf. Sci. 357 (2015) 696–703.
[58] D. Wang, G. Fang, T. Xue, J. Ma, G. Geng, A melt route for the synthesis of activated carbon derived from carton box for high performance symmetric supercapacitor applications, J. Power Sources 307 (2016) 401–409.
[59] M. Zhi, F. Yang, F. Meng, M. Li, A. Manivannan, N. Wu, Effects of pore structure on performance of an activated-carbon supercapacitor electrode recycled from scrap waste tires, ACS Sustainable Chem. Eng. 2 (2014) 1592–1598.
[60] L. Zhang, T. You, T. Zhou, X. Zhou, F. Xu, Interconnected hierarchical porous carbon from lignin-derived byproducts of bioethanol production for ultra-high performance supercapacitors, ACS Appl. Mater. Interfaces 8 (2016) 13918–13925.
[61] J. Houa, K. Jiang, M. Tahir, X. Wu, F. Idrees, M. Shen, C. Cao, Tunable porous structure of carbon nanosheets derived from puffed rice for high energy density supercapacitors, J. Power Sources 371 (2017) 148–155.
[62] B-O. Park, C. D. Lokhande, H-S. Park, K-D. Jung, O-S. Joo, Performance of supercapacitor with electrodeposited ruthenium oxide film electrodes-effect of film thickness, J. Power Sources 134 (2004) 148–152.
[63] M. D. Stoller, R. S. Ruoff, Best practice methods for determining an electrode material's performance for ultracapacitors, Ener. Environ. Sci. 3 (2010) 1294–1301.
[64] M. D. Stoller, S. Murali, N. Quarles, Y. Zhu, J. R. Potts, X. Zhu, H-W. Ha, R. S. Ruoff, Activated graphene as a cathode material for li-ion hybrid supercapacitors, Phys. Chem. Chem. Phys. 14 (2012) 3388–3391.
22
[65] T. Kesavan, R. Aswathy, I. Arul Raj, T. P. Kumar, P. Ragupathy, Nitrogen-doped graphene as electrode material with enhanced energy density for next-generation supercapacitor application, J. Solid State Sci. Tech. 4 (2015) M88–M92.
[66] G. P. Pandey, S. A. Hashmi, Y. Kumar, Performance studies of activated charcoal based electrical double layer capacitors with ionic liquid gel polymer electrolytes, Ener. Fuels 24 (2010) 6644–6652.
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Figure Captions:
Table 1. Comparing the performance of various bio-waste based NAC electrode used for supercapacitor applications.
Scheme 1. Schematic illustration of the synthesis of the NAC materials.
Fig. 1. (a) Powder X-ray diffraction patterns of NAC material prior to- (black curve) and after activation (red curve); (b) FT-IR spectra of the developed NAC material prior to- (black curve) and after activation (red curve); (c) Raman spectra of the developed NAC material prior to- (black curve) and after activation (red curve); (d) BET N2 adsorption-desorption isotherm of NAC material (Inset: The corresponding pore size distribution profile).
Fig. 2. (a-c) TEM images and (b) SAED pattern of the NAC material.
Fig. 3. XPS spectra of (a) survey scan, (b) C 1s, (c) O 1s and (d) N 1s of the NAC material.
Fig. 4. (a) CVs of the NAC electrode prior to- (black curve) and after activation (red curve) at a scan rate of 20 mV s-1. (b) CVs of the NAC electrode at various scan rates. (c) Galvanostatic charge-discharge profile of the NAC electrode prior to- (black curve) and after activation (red curve) at a current density of 1.7 A/g. (d) Galvanostatic charge-discharge profile of the NAC electrode at different applied current densities.
Fig. 5. (a) Dependence of specific capacitance on various current densities and (b) Ragone plot of the NAC electrode in three electrode system. (c) Cycle life of the NAC electrode recorded at a current density of 1.7 A/g. (d) EIS spectra of fresh (block curve) and after cycled NAC electrode (red curve).
Fig. 6. (a) CVs of the NAC electrode as an electrolyte at different scan rates. (b) Galvanostatic charge-discharge profile of NAC electrode at different current densities. (c) Specific capacitance as a function of different current density and (d) Ragone plot of the NAC in two electrode system.
Fig. 7. (a) Cycle life of the NAC electrode at a current density of 0.35 A/g and (c) EIS spectra of the NAC electrode fresh (red curve) and after had a cycled electrode (black curve).
24
Table 1.
S.No Carbon Source
Specific Capacitance
(F g-1)
Current density (A g-1)
Electrolyte Cycle Life
Energy Density
(Wh kg-1)
Power Density (W kg-1)
Ref.
1 Rice husk 147.0 0.1 6M KOH 10000 5.11 - 52 2 Rice bran 265.0 10.0 6M KOH 10000 70.0 1223.0 53 3 Bagasse
waste 320.0 0.5 1M Na2SO4 15000 20.0 182.0 54
4 Bamboo char
222.0 0.5 6M KOH 5000 20.6 12000.0 55
5 Food waste 106.0 1.0 mA 3M KOH 500 - - 56 6 Waste tea 203.0 1.5 mA 1M H2SO4 400 - - 57 7 Carton box 311.0 0.5 6M KOH 5000 10.8 125.0 58 8 Waste tire 106.0 1.0 6M KOH 1000 - - 59 9 Lignin 312.0 1.0 6M KOH 20000 44.7 - 60 10 Puffed rice 334.0 0.5 6M KOH 11000 104.0 - 61 11 ICR 381.0
217.0
1.7 0.35
1M H2SO4 1M LiPF6
6000 10000
- 47.1
- 22644.0
This work
25
Scheme 1
26
Fig. 1
27
Fig. 2
28
Fig. 3
29
Fig. 4
30
Fig. 5
31
Fig. 6
32
Fig. 7
33
Graphical Abstract
Hierarchical nanoporous-structured activated carbon directly derived from “Indian Cake Rusk” food waste exhibits high specific capacitance of 381.0 F g−1 at current density of 1.7 A g−1 after 6000 cycles in aqueous electrolytes under three-electrode set up, while 47.1 Wh Kg−1 and power density of 22644 W Kg−1 in non-aqueous electrolyte with two electrode configuration.